There are currently three established technologies for the production of electricity from biomass—pyrolysis, gasification, and direct combustion. These are already discussed at length in Sect. 1.2.1.1 Direct combustion is the oldest method for electricity generation from biomass where complete oxidation of biomass in presence of excess air is done to produce carbon dioxide and water. Hot flue gases are used to heat the process water to steam, which can be used to drive a turbine resulting in production of electricity. This is not a very efficient method of elec­tricity generation when compared to pyrolysis and gasification. Pyrolysis involves the thermal destruction of biomass under anaerobic conditions without the addition of steam or air resulting in the production of gases and condensable vapors. Combustion of these gases is done in a gas turbine resulting in generation of electricity. This method is more efficient than direct combustion but requires more process control and investment. The gasification method comprises controlled addition of steam to the biomass resulting in partial oxidation of the biomass to produce combustible gases which have a high calorific value. These gases are fed to a combined gas turbine to produce electricity. This method, like pyrolysis is
more efficient than direct combustion but requires more process control and investment. The carbon emissions produced as a result of electricity generation from biomass are much lower than the other energy counterparts. The highest carbon emissions during electricity generation from biomass is reported to be 60 g CO2 equivalent/kWh, which is less than one-third of the lowest CO2 emission during electricity produced from natural gas and one-fifth of the lowest CO2 emissions produced from a coal — fired power station [57].